1. Technical Field
The present invention relates to an inertial sensor and a method of manufacturing the same.
2. Description of the Related Art
Recently, an inertial sensor has been used in various fields, for example, the military, such as an artificial satellite, a missile, an unmanned aircraft, or the like, vehicles, such as an air bag, electronic stability control (ESC), a black box for a vehicle, or the like, hand shaking prevention of a camcorder, motion sensing of a mobile phone or a game console, navigation, or the like.
The inertial sensor generally adopts a configuration in which a mass body is bonded to a flexible substrate such as a membrane, or the like, so as to measure acceleration and angular velocity. Through the configuration, the inertial sensor may calculate the acceleration by measuring inertial force applied to the mass body and may calculate the angular velocity by measuring Coriolis force applied to the mass body.
In detail, a process of measuring the acceleration and the angular velocity by using the inertial sensor will be described in detail below. First, the acceleration may be obtained by Newton's law of motion “F=ma”, where “F” represents inertial force applied to the mass body, “m” represents a mass of the mass body, and “a” is acceleration to be measured. Therefore, the acceleration a may be obtained by sensing the inertial force F applied to the mass body and dividing the measured inertial force F by the mass m of the mass body that is a predetermined value. Meanwhile, the angular velocity may be obtained by Coriolis force “F=2 mΩ·v”, where “F” represents the Coriolis force applied to the mass body, “m” represents the mass of the mass body, “Ω” represents the angular velocity to be measured, and “v” represents the motion velocity of the mass body. Among others, since the motion velocity v of the mass body and the mass m of the mass body are values that are known in advance, the angular velocity Ω may be obtained by sensing the Coriolis force (F) applied to the mass body.
As described above, when the inertial sensor measures the acceleration a, the mass body is displaced by the inertial force (F). In addition, when the inertial sensor measures the angular velocity (Ω), the mass body needs to be vibrated at the motion velocity v. As described above, in order to measure the acceleration “a” or the angular velocity (Ω), the mass body needs to be moved and the bottom portion of the mass body is provided with a cap so as to protect the moving mass body.
FIG. 1 is a cross-sectional view of an inertial sensor according to the prior art. As shown in FIG. 1, an inertial sensor 10 according to the prior art is configured to include a membrane 1, a mass body 2, a post 3, and a cap 4. In this configuration, a gap G between the mass body 2 and the cap 4 affects dynamic characteristics of the inertial sensor 10 in connection with a damping force of air for the mass body 2. The gap G between the mass body 2 and the cap 4 is affected by a thickness of an adhesive 5 that bonds the post 3 to the cap 4. However, a generally used adhesive 5 has low viscosity, such that it is difficult to control the thickness of the adhesive. As a result, it is very difficult to precisely implement the gap G between the mass body 2 and the cap 4. As such, when the gap G between the mass body 2 and the cap 4 is not precisely implemented, the dynamic characteristics of the inertial sensor 10 may be deteriorated.
In addition, when the post 3 and the cap 4 are bonded to each other so as to thinly implement the adhesive 5, the adhesive 5 having low viscosity is permeated into the post 3 when pressing the post 3 and the cap 4. As such, when the adhesive 5 is permeated into the post 3, a space (S) between the mass body 2 and the cap 4 is reduced and thus, the damping force of air for the mass body 2 is changed, thereby deteriorating the dynamic characteristics of the inertial sensor 10 and causing dispersion changing quality during mass production. In addition, when an amount of the adhesive 5 permeating into the post 3 is increased, the adhesive 5 is directly bonded to the mass body 2, thereby causing the defects of the inertial sensor 10.